Method of cleaning the inside of pipe



May 15, 1956 c. A. PRINCE METHOD OF CLEANING THE INSIDE OF PIPE FiledApril 12, 1954 INVENTOR Char/e5 A Pr/n 06 ATTORNEYS.

United States PatentO 2,745,231 METHOD OF CLEANING THE INSIDE OF PIPECharles A. Prince, Shreveport, La., assignor to The Dow ChemicalCompany, Midland, Mich., a corporation of Delaware Application April 12,1954, Serial No. 422,525?

Claims. (Cl. 51- 282) The invention relates to a method of cleaning theinside of pipe. It more particularly concerns an improved method ofcleaning the interior of a pipe in which scale or like incrustations aredislodged and carried out of the pipe by means including a particulatedabrasive in suspension in a liquid vehicle. a

The various methods which have been proposed and used heretofore ofremoving scale and the like from the interior surface of pipe may beclassified in three groups as follows: (1) Methods involving the use ofsolvents. In these methods, a liquid solvent, which may also chemicallyattack the deposits, is introduced into the pipe and left in contactwith the deposits until dissolved or sloughed oif. The success of thesemethods depends upon the effectiveness of the solvents to eitherdissolve or react chemically with the deposits so as to convert them tosolubles. Since not all deposits found, in pipes" arev amenable tochemical attack or solvent action, these methods have limitedapplication. Other disadvantages are that the solvent method usuallyrequires filling the pipe withsolvent which may be prohibitively costly,and the solvent action is oftentimes slow and may be damaging to thematerial of the pipe. (2) Methods involving the use of scrapers and likescale dislodging devices which are caused to traverse the bore of thepipe. Various limitations inure to these devices, such as therequirement that the pipe be of uniform diameter and smooth bore,thatjoints in the pipe be smooth and internally ofthe same diameter asthe pipe itself, and that the pipe be reasonably straight and withoutsharp turns. (3) Methods using high velocity jets of liquid directedagainst the scale.

' 2,745,231 Patented May 15, 1956 Fig. 3 is a cross section on the line33 of Fig. 1.

Figs. 4, 5, and 6 are elevations partly in section of threemodifications, respectively, of the bore constricting object used in thepipe line of Fig. 1.

Fig. 7 is a cross section on any one of the lines 77 of Fig. 6.

Referring to the drawing in detail, numeral 1 indicates a pipe linehaving a cylindrical bore on the interior of which is a layer of scale 2to be removed in accordance with the invention. As shown one end of thepipe line is provided with a pipe flange 3 to which is attached the lockchamber 4 by bolts 5. The lock chamber 4 is connected by a pipe 6 to thedischarge side of a force pump 17. The intake side of the forcepump isconnected by pipe 8 and valve 9 to the outlet 10 of mixing tank 11 whichis provided with a motor driven agitator 12.

In canyingout the invention, an abrasive-laden liquid I is prepared, orplaced, in tank 11 and preferably main- In such methods, they nozzlesfor the jets are'carried by an apparatus, usually referred to as a mole,which is attached to a hose that supplies the liquid to the nozzles. Thereaction from the jets causes the mole to traverse the bore of the pipe.These methods have similar disadvantages to those under (2) and aregenerally limited to use in short pipes of moderate diameter as thereare limitations to the ability of the jets to drag the hose.

An object of ,the invention is to provide a-me'thod of cleaning the.inside of pipe which need not be restricted as to length or diameter.

An object of the invention is to provide a method of j V cleaning ,theinside of, pipe which need not beproof against "attackby acidsor.alkalies.-.. 1'

A further object of the invention is to provide a method bends andturns.

Still another object of the invention is to provide a method of removingfrom the inside of pipe soluble as well as insoluble scale or likeincrustations.

The foregoing and related objects will become apparent from thefollowing description of the invention taken in connection with theaccompanying drawing.

In the said drawing, Fig. 1 is a side elevation of a portion of a pipeline and apparatus used therewith in the practice of the invention in apreferred form.

Fig. 2 is a cross section on the line 22 of Fig. 1.

tained in an agitated state by means of agitator .12. Preparation of theabrasive-laden liquid may be accomplished by mixing a suitableparticulated abrasive solid with a suitable liquid vehicle capable ofkeeping the particles from too rapidly settling when the mixture is notundergoing agitation. Suitable abrasive materials are crushed stone,steel,Ior ceramics, sand, fine gravel, and the like. A generallysuitable abrasive is sand of 20 to 40 v mesh sieve size, although othersizes of abrasive particles may be used, such as from inch to 150 mesh.Suitable vehicles are petroleum oils or other neutral liquids withconsiderable viscosity such as from 20 centipoises to 30,000centipoises. Water or brine which has been thickened by the admixture ofa suitable thickening agent may be used. Pumpable emulsions of oil andwater are especially suitable for they readily maintain the abrasiveparticles in suspension usually without agitation once the abrasiveparticles and the emulsion are well mixed. An acid maybe added to. the.water or water-oil emulsions, if desired, to give the vehicle theability to dissolve acidsoluble constituents of the deposits to beremoved. Among the thickening agents which may be used to increase theviscosity of water are water-soluble gums, e. g. gum arabic, karaya;starches; gelatin; sugarsyrups; cellulose ethers, e. g. methylcellulose, carboxy methylcellulose; and the like. Oils may be thickened,if necessary,

tired or synthetic rubber, salts of fatty acids, and the like.

9 The amount of thickening agent touse varies with the kind and theliquid involved and is readily determined by test as by mixing thethickeningagent with the liquid to liquid vehicle therefor does notappear to .be' sharply critical. For example,.there may be used fromabout 0.1

of cleaning the inside of pipe line which may include;

to 5 pounds of the abrasive per gallon of liquid vehicle. Preferredconcentrations are between 0.25 and 3 pounds .of abrasive particles pergallon of vehicle.

' In applyingthe method to apipe line, there is inserted into the. pipea generally spherical rigid object having a diameter slightly less thanthe inside diameter of. the clean spherical object may be used as forexample a smooth sphere such as a solid or hollow steel ball, asillustrated in Fig. 1, and is useful in pipes in which the scale to bere moved is of irregular thickness. Another form is illustrated in Fig.4 in which the surface of the spherical object is provided with dimples13. These may be in the form of more or less spherical recesses having,for example, a radius of 0.1 to 0.4 of that of the object. The formillustrated in Fig. is generally spherical, the surface of which isprovided with stubby conical projections 14. The forms of boreconstricting objects illustrated in Figs. 4 and 5 are especiallysuitable for scale deposits of uniform thickness, although they may beused with depos its of irregular or uneven thicknessl' These generallyspherical bore constricting objects may be advantageously perforatedwith passageways extending diametrically through the object. One form ofperforated spherical object is illustrated in Fig. 6 havingdiametrically disposed passageways 15.

Insertion of the bore constricting objectinto the pipe to be cleaned isfacilitated by lock chamber 4 which is detached from the pipe line andthe object inserted into the space 16 as indicated at 17. The lockchamber'with the bore constricting object in it is then attached to thepipe line by means of the flange bolts 5 as shown in position in Fig. l.

Abrasive-laden liquid 18 maintained in a state of agitation, ifnecessary, by agitator 12 in tank 11 is then pumped therefrom, whilevalve 9 is open, by pump '7 into the lock chamber 4, thereby forcing thebore constricting object 17 from the lock chamber into the pipe line 1where it encounters the scale deposit 2. Scale removing action thendevelops. This results from the pumping pressure applied to theabrasive-laden liquid and the action of the bore constricting objectwhich directs the abrasive-laden liquid into the annular space 19forming an abrasive liquid jet against the scale which, in the caseillustrated, is generally of irregular thickness as shown in Fig. 3.letting thus occurs at the places, e. g. 20, where the bore constrictingobject is not in actual contact with the scale. -As jetting and abrasionof the scale continues, the parts of the scale in contact with the boreconstricting object, e. g. 21, wear away allowing the object to move on.As the scale is thus dislodged, the bore constricting object moves alongthe pipe leaving it substantially scale free.

Although a bore constricting object having a smooth surface, such as asphere generally operates well, as shown in Figs. 1, 2, and 3, themodifications illustrated in Figs. 4, 5, and 6 have the advantage thatthere is little or no danger of them hanging up in the pipe in the eventthat the scale is of such uniformity of thickness as not to permit theabrasive liquid to pass at any point between the surface of the boreconstricting object when smooth and the interior of the pipe. It ismanifest that by dimpling the surface of bore constricting object, as inFig. 4, or by providing projections, as in Fig. 5, space is therebyprovided for passage of abrasive liquid between the surface of the boreconstricting object and the scaled pipe so that scale removal by jettingand abrasion isobtained irrespective of the uniformity of thickness ofthe scale layer. With the modification shown in Fig. 6, jetting actionis assured at all times by the passageways 15 which also have theadvantage of directing additional jets of abrasive liquid against thescale irrespective of the orientation of the bore constricting object.

Since the bore constricting object is only slightly smaller than thebore of the pipe to be cleaned, it does not advance through the pipebeyond where the scale is so that complete removal of scale is assuredas the bore constricting object traverses the pipe.

The following example is illustrative of the invention:

Example A pipe line feet long with an inside diameter of 4.25 incheswas. incrusted with a layer of scale about 0.0625 inch thick. To one endof the pipe line was attached a short length of clean pipe of the samediameter containing a smooth steel ball 4.125 inches in diameter. Anabrasive liquid mixture, formed by mixing water with gum karaya in theproportions of 0.3 pound of gum and 2 pounds of 20-40 mesh sand pergallon, was pumped into the clean portion of the pipe behind the ball soas to drive it into the scaled pipe using an injection rate of 10gallons per minute of the sand-laden thickened liquid. The pressurevaried during the injection but did not exceed about 250 p. s. i. As theinjection continued movement of the ball along the pipe could bedetected from the noises which were emitted as jetting and scale removaltook place adjacent to the wall. The ball did not move at a uniform ratebut remained in some locations longer than others in its journey throughthe pipe. About 200 gallons of the sand-laden thickened liquid wereintroduced into the scaled pipe before the ball emerged from the pipe atwhich time approximately 98 gallons of the abrasive-laden thickenedliquid had by-passed the ball. Examination of the pipe after the ballhad traversed the length of the pipe and emerged from it indicatedsubstantially complete removal of the scale.

I claim:

1. The method of dislodging scale from insid'e'a pipe line having agenerally uniform diameter cylindrical bore which comprises insertinginto the pipe line at one end a generally spherical rigid object havinga diameter slightly less than that of the inside of the pipe line andintroducing into the pipe line behind the said object an abrasive-ladenliquid under pressure so as to force the abrasive liquid between thesaid object and the inside of the pipe line to produce jetting andabrasion against the scale and move the said object along the bore ofthe pipe line as the scale is thereby dislodged.

2. The method according to claim 1 wherein the said rigid object is asmooth sphere.

3. The method according to claim 1 in which the said rigid object is asphere having a dimpled surface.

4. The method according to claim 1 in which the surface of the saidrigid object is provided with stubby projections.

5. The method according to claim 1 in which the said rigid object isprovided with a plurality of passageways passing therethroughdiametrically in various directions.

References Cited in the file of this patent UNITED STATES PATENTS597,185 Huebner Jan. 11, 1898 1,415,600 Mannion et al May 9, 19221,475,431 Evans Nov. 27, 1923 1,808,870 Strasburg June 9; 1931 2,087,694Malmros July 20, 1937 2,382,262 Scherer et al Aug. 14, 1945 2,478,961Wortham Aug. 16, 1949 2,605,596 Uhri Aug. 5, 1952 2,668,307 Preen Feb.9, 1954

